The invention relates to a key/vehicle communication device of the type which can activate an arrangement for immobilizing the vehicle, as well as other remotely controllable functions.
Electronic immobilizers for protecting a vehicle against unauthorized use (that is against being started up without permission) are known. In such devices, the inductive key/steering-column lock communication channel constitutes a very short-range radio transmission link which deactivates the immobilizing function when the electronic key is inserted into the steering-column lock. The ensuing check of a use authorization code stored in the key confirms that the key is the one authorizing the use of the vehicle. One known embodiment of such an arrangement involves a so-called transponder which is arranged in the key, and contains the use authorization code in retrievable form.
An additional vehicle-side function, which can also be activated by remote control, may be, for example, an access protection function, such as a central locking system and/or a break-in/theft warning system, which is activated via a key/vehicle communication channel, by actuating a key-side actuating member. The range of this communication channel is designed to be greater than that of the inductive key/steering-column lock transmission link, so that the relevant function (for example, the access protection function) can be activated or deactivated at an early stage by means of a key located outside the vehicle.
German patent document DE 43 40 260 A1 discloses an ignition-key/vehicle communication device, in which a key receptacle for receiving a key contains an additional switch. When the key inserted, the switch is actuated via a tappet, and switches on inductive energy transmission for an energy store of the key. Subsequently, a use authorization check is performed by means of a bidirectional code data exchange via a key/lock communication channel with an infrared transmission link, using a changeable code for the purpose of approving the operation of an electronic key. In addition, a central locking system and/or an alarm system can be activated via a key/vehicle communication channel. The latter can also respond by remote control from outside the vehicle by means of corresponding key actuation.
In devices of this type, there is generally a risk of improper operations due inadvertent actuation of the key-side actuating member for the remotely controlled activation of a vehicle-side function (such as the access protection function, for example). Such improper operation of this kind is particularly likely to occur when the key is inserted into the ignition lock and the engine is started or stopped by turning the key, since such handling of the key may unintentionally lead to the actuation of the actuating member.
In order to decreases the risk of such unintended actuations of an opening button and a closing button arranged on an electronic vehicle key (and thereby accidentally triggering the locking or unlocking of vehicle doors by remote control), German Patent Document DE 42 38 042 A1 discloses a particular arrangement of these actuating members on the key. In particular, either the opening button is covered by a key bit articulated for swing action on the key bow part, in the swung-in state of the said key bit, or the opening and closing buttons can be operated only indirectly by pressing on the swung-in or swung-out key bit.
U.S. Pat. No. 4,383,242 discloses an ignition-key/vehicle communication device for the activation of a vehicle protection system which comprises an immobilizing function and an access protection function. The access protection function, in turn, comprises a door locking system and a break-in/theft warning system. In this device, before getting into the vehicle which has an armed protection device, the user can actuate a transmitter button on an electronic key, thereby triggering a remote-control signal which releases the door locks, disarms the break-in/theft warning system, and deactivates the immobilizing function (which otherwise disables the ignition when an attempt at unauthorized access is recognized). When the user leaves the vehicle, these three functions can be activated once again, and the protection device thus armed, by actuating the transmitter button again.
In order to avoid arming the device by unintentionally actuating the transmitter button on the key during starting of the vehicle or during its subsequent running (which, in the latter case in particular, would cause an undesirable interruption of ignition), activating signals transmitted from the key and received on the vehicle side are logically combined in an OR gate with a signal representing the state of ignition, so that the activating signals are ignored when the ignition is switched on.